I am getting some tearout on router table using a grooving bit on CVG Douglas Fir. Bit is sharp. I know fir can be brittle. Am I better going with a faster or slower motor speed. I am right in the middle now.
Just made a sample pass and quit for the day. Figured my gurus would assist. Thanks.
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Replies
Fir can be brutal that way. First thing to do is read the grain and run the material so the cutter is not lifting the grain (think of petting a dog the right way). It helps if your groove cut is absolutely centered so you can run the material upside down if need be. This will mean that all the material has to be exactly the same thickness. Some boards will have grain that runs in AND out on the same edge, and you may not be able to get a clean groove no matter what, using a router. If you are able to make your cuts using a tablesaw and dado blade you may have a lot easier time--the much larger diameter of the blade means the exit angle is a lot shallower and there should be little if any tearing. Part of the problem with router bits sometimes is that they are so small and the exit angle is too steep. Same with jointers and even shapers sometimes.
What Dave said. Fir is terrible for that. Speed is not so much the issue as is chip load. Take more passes, and less chip load.
Often climb cutting is used, but without MUCH exp. and the right cutters, you best not try. Depending on what exactly is your 'Grooving' bit , may not make a difference, I envision a groove like a V or a U...I don't know what you are doing.
If indeed youare making a V or a U half of the cutter is going against the grain or even across the grain..and Fir HATES that.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations
They kill Prophets, for Profits.
It's tongue and groove bits. The tongue (on rails) went well. Unfortunately, the groove isn't centered because I have a thick panel going in that will be rabbetted, and it needs to be flush with back of door.Maybe I will do multiple passes. Will different speed do anything?
Edited 3/25/2009 4:22 pm ET by Tom69
You'd want highest cutter speed and slow enough feed speed that it don't burn. Light passes, don't do it all in one pass.Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations
They kill Prophets, for Profits.
"Maybe I will do multiple passes."No maybe about it if you want to reduce the splintering
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I'd multiple climb cuts. If you don't do climb cuts you will lift the grain and when you lift VG doud fir it will go down the the whole board.
I have glued pieces back. Or cut them off. They just keep going if you don't.
Before I'd suggest a climb w/out a powerfeed or a lot of practice, I'd suggest making stopping cuts by nipping away from the end then finish with full pass.
Climb with a cope and stick cutter is dangerous with a feeder, and almost suicidal without.Spheramid Enterprises Architectural Woodworks
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You are right. It is an advanced move. I was thinking you could make mutiple passes so the cuts were really small. The depth of cut would be just say a 1/16". It would be time consuming but it would work.
I trimmed a house in vg doug fir and I would get these long splinters that just kept going unless I cut them off with a knife or glued them down and came back later. And that was not milling anything.
Just send that pesky old vg fir (have to bow my head when I say that) out this way. I LOVE that stuff. Love the grain, the colors, the strength, the stability...even have come to love machining it.
"Can't get enough, of that funky stuff"
Yessir, yessir. Send that stuff out my way.
Climb cutting? Please explain that.
Ok...Climb cutting is a potentially dangerous technique of feeding the stock from the "Wrong" side so the cutter wants to pull the board away from and push it away from the fence.Best done with a power feeder and with light passes.BUT...as I understand your description, you are cutting stub tenons on the ends of door stiles?Yes??then first you need to back up your work-piece with a sacrificial fence on your miter gage.You ARE using a miter gage or some other type of guide to run a short end grain thru a router....Aren't you???and light passes will help also.if you need some detailed explanation, this has probably been discussed ad nauseum over on the knots forum...have fun!!and oh yeah...Be CAREFUL out there!!!(;o)>.
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"Climb cutting"?
I do it all the time, but not usually across the grain, like when milling the tennons for cope and stick joinery. I'm more likely likely to climb cut paralell to the grain of the board, more of an edge forming technique.
Anyways, like Mr T said, I feed the stick into the router (or shaper) the opposite direction of normal, so that if the router is handheld, the router wants to "climb".
The advantage to climb cutting is that the leading flute slices towards the board, instead of away from it so you get way less tearout. But the disadvantage is it is harder to control the tool, therefore less safe, potentially VERY dangerous.
You have to understand the way the bit is spinning, the way it is cutting.
Climb cutting is similar to feeding a board into a tablesaw from the wrong side of the saw, or running a Skilsaw backwards, so the spinning of the blade wants to make the saw climb up out of the cut.
"very dangerous"
Yeppers. Thats why another safer way is nibble the end and then move ahead and nibble again, until the grain is sufficiently relieved along the length, then do a full pass.
Like handplaning a moulding, you start the profile at the farthest away end, and then drop back, and drop back again, and repeat till you can take a full pass.
Crosss grain copes, you just gotta deal with it, and have a decent backer.Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations
They kill Prophets, for Profits.
The cross grain tenons went fine. I kept the stock full width and clamped to a sled with sacrificial fence. Then ripped multiple rails.For stiles I will try multiple passes starting from rear end. If that doesn't work too well it will be full length shallow passes.
one thing I try to do with wood that likes to tear out is - take some of the meat off with a tablesaw and use the router for the finish pass. Can also work on big roundovers, raised panels, etc. We did some heart pine entry doors years ago (on a shaper), and got tired of those pointy shards hitting us in the forearms. Finally ripped off most of the waste and then ran them. Much better.
Great suggestion! I'm definitely trying that,